The present invention is related to roadway barriers and safety systems, and more particularly, to a roadway guardrail system having a rail and a plurality of support posts.
Along many roadways it may be hazardous for a vehicle to leave the roadway. As a result, roadway safety barriers, including guardrail systems, are used along roadways. The guardrail systems may act to contain and redirect an errant vehicle along such roadways. Such guardrail systems may dissipate some of the vehicle's energy through deformation of the rail or post, or both.
A guardrail system in the past may have included a plurality of rails secured to a plurality of support posts made of wood or steel. One type of rail was the “W-beam,” which is a guardrail named after its characteristic shape. Other railing configurations such as thrie beams and box beams were also used. Support posts may have been made of wood, metal or a combination of both.
Wooden support posts had several drawbacks. Wooden support posts were susceptible to deterioration from environmental exposure. As a result, wooden posts may have been treated with certain chemicals to slow deterioration, but such chemical treatments created additional expense in handling and in disposing of the treated wood. Wooden support posts also may have been installed in foundation sleeves or concrete foundations, while adding material costs and labor costs that resulted in a more expensive installation. Moreover, the same chemicals that aid in prolonging the life of the wooden posts can make the disposal of the posts on replacement a hazardous waste.
The trend has been toward using steel support posts, rather than wooden support posts, due to savings in material cost, durability, reliability, and maintenance. Steel posts have been installed by driving the posts directly into the ground, with or without a foundation sleeve as desired. Steel posts also could be treated to slow the effects of environmental exposure from rust and the like.
For improved safety, break away steel support posts that allow for failure during a collision have been developed. However, the design of breakaway steel support posts has remained relatively unchanged over the years. Such break away designs in the past may have had I-beam posts with cutouts or apertures along a portion of the post. At least some of the cutouts could be sized to receive fasteners for coupling the guardrail beam to the post. Other designs had the post in two sections joined with rotatable or releasable couplings that connected the two sections of the post and failed upon a sufficient impact force. However, such prior steel posts required substantial time, money, and resources during fabrication, modification, and installation.
The state of the art in guardrail systems has been documented and applied through specifications used by the industry. The United States Department of Transportation Federal Highway Administration provides “Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects,” including a section for guardrails and support posts. Industry groups such as the American Association of State Highway and Transportation Officials AASHTO, the Associated General Contractors (AGC) of America, and the American Road & Transportation Builders Association ARTBA have developed “A Guide to Standardized Highway Barrier Hardware” that included specifications for guardrails and posts. These specifications teach a guardrail system having a guardrail bolted to a large wood post or a large I-beam steel post. In general, in the past larger posts in guardrail systems better withstood impact forces to redirect a vehicle along the direction of the roadway.
A roadway guardrail system is presently disclosed to dissipate a portion of an impacting vehicle's energy and enable an impacting vehicle to be redirected by the system. The roadway guardrail system may be installed adjacent a roadway, such as along median strips, roadway shoulders, or any other path that is likely to encounter vehicular traffic.
The disclosed roadway guardrail system may comprise a rail having a plurality of mounting apertures, a plurality of support posts each having a slot extending along a portion of the length of the post such that a portion of the slot aligns with a rail mounting aperture at a desired height, and a plurality of fasteners each capable of fastening the rail to more than one support post through the slots and the mounting apertures to support the rail with the posts, such that upon a vehicle impact with the rail the fasteners are adapted to slide along the slot in the support post.
Alternatively, the disclosed roadway guardrail system may comprise a plurality of support posts each having a mounting aperture, a rail having laterally extending slots traverse the length of the rail such that a portion of a slot aligns with a post mounting aperture at a desired rail height, and a plurality of fasteners capable of fastening the rail to the posts through the laterally extending slots and the mounting apertures to support the rail with the posts, such that upon a vehicle impact with the rail the fasteners are adapted to slide along the slots in the rail.